Electrocoating is a process wherein a film-forming resin having an electric charge is dispersed in an aqueous medium and electrophoretically moved onto an electrical conductive substrate when a voltage is applied between the substrate and the other electrode to form a deposited film on the substrate. In this process, it is difficult to electrocoat two or more times to obtain a thick film, because the deposited film during electrocoating is an insulating film so as to inhibit its electrical conductivity.
In order to ensure the electrical conductivity of the deposited film, it has been proposed that a material having electrical conductivity, such as metal or carbon powder, be formulated into the electrocoating composition. It, however, is required to add the electrically material conductive to the coating in a large amount to obtain a sufficient conductivity, thus remarkably deteriorating the film properties.